Rate of climb instruments



Feb. 9, 1937. A. URFER RATE OF CLIMB INSTRUMENTS original Filed April 9, 195o M IMHN Reawed ret. 9, 193'/ UNITED STATES i Re. 20,263

' aan: or chum ms'rnmm's Adolf Unef, New nathalie, N. Y., .maar in Pioneer Instrument Company.

Incorporated,

Brooklyn, N. Y., a corporation ol New York Original No. llyhiell February 25, 1936, Serial No. 442,720, APl'll 9, 1,930. Application for reime 1022437 lsclailns.

This invention relates to rate of climb instruments. A simple form of rate of climb instrument may be described as having a diaphragm chamber which communicates with the atmos- 5 phere through a restricted orifice similar to a capillary tube. As the instrument is subjected to changing pressure conditions, the pressure within and without the 'diaphragm chamber tends to become equalized by the ilow oi air 1u' through the capillary tube. The rate of iiow of air through the capillary tube under changing pressure conditions is a function of the rate of change of pressure taking place. The movement ot an indicating hand which has connection with l5 the yielding wall of such a diaphragm chamber may be used to give an indication of the rate of change of altitude taking place when such an instrument is carried by an aircraftin ascent or descent.

l80 climb instrument so as to ailord greater accuracy oi indication over wide ranges of temperature changes. 'y

Other objects and advantages will be pointed out hereinafter in the description of the invention and illustrated in the drawing, in which, Fig. I is a section through a rate of climb instrument showing the working elements thereof and embodying the preferred construction of my invention;

Fig. 1I is a detail on line II-II of Pig. I; and

Pig. III illustrates a modified form or device Vfor accomplishing the purpose of the present invention. n

It is a common practice to mount a diaphragm chamber I0 within another chamber formed by a casing il. This .second chamber or interior of casing il is subjected to atmospheric pressure at all times. The/casing il preferably is made vairtight but it is'prcvided with a vent i2 by means of which it is placed in communication with the atmosphere in a region wherenormal atmospheric conditions exist` TheI particular vent connection illustrated has a member Il to which may be connected. by a union il, amember il having openings Il. This connection maybe Among the objects of the present invention is September 24, 1938, Serial No.

used in instances where the atmosphere about an instrument or in the vicinity of the vent is subjected to normal atmospheric pressure conditions at the altitude at which. the aircraft is traveling. In the event-that it is desired to vent the interior of the casing at a remote point, the member I5 may be replaced by a -tube extending to a remote place. It is at once apparent that the chamber surrounding the diaphragm chamber and defined, in the present instance, by casing Ii may be of limitless extent vso far as the usefulne of the present invention is concerned.

Referring to the construction illustrated herein, pillar Il which extends from the wall i9 of the instrument supports the spring element 20 upon which is mounted the diaphragm chamber i0. kOne end of 'the diaphragm chamber III is malntained in a xed position by ,an adjusting screwA 2| Vwhich engages the free end of theelement 2l.

The interior of the diaphragm chamber Il communicates with the atmosphere through a capillary tube 22. The capillary tube is supported from the wall of a chamber 2l which has free communication with the diaphragm chamber through conduit 2i and a hollow lug 24a. Also communicating with chamber 23, through conduit Il, is a heat insulated tank 20. This-heat insulated tank is usually provided and its purpose it to increase the effective volume of air whose pressure is affected by the conilned air active from within the diaphragm chamber Il. When the instrument is at a given pressure for any length of time, the same pressure prevails on the inside as well as the outside of the diaphragm chamber il and in tank 2l inasmuch as the diaphragm chamber is connected to the outside air by means of the capillary tube 22 and the casing vent I2. If now the aircraft ,carrying `l.the instrument starts to climb, Ait immediately lgets into air of lower pressure. This pressure becomes the pressure on the outside of the diaphragm chamber I0 because of air escaping through the vent l2. The air inside the diaphragmchamber and in the tank 2i is, however. only at the pressure corresponding to the previous altitude inasmuch as the pressure of the volume of air in the diaphragm chamber and the tank cannot equalize immediately due .to the small opening through the capillary tube through which the diaphragm chamber and the tank 2t' sure diiIerenc'e thus produced causes a-n expansion of the diaphragm and, hence, the pointer 28 is moved` to indicate a climb. \As previously stated, the heat insulated tank 25 is provided for the purposeof increasing the eective volume of enclosed air active 'from within -the interior ofthe expansible diaphragm chamber I0. Q The rate of ow of air through the capillary tube during a changev inelevation is a functionl of the rate oi change or pressure which is taking piace as the aircraft ascends, and hence a function of the rate of change of altitude which produces the rate of change oi pressure.

' In order to indicate the change of altitude occurring the motion of the yielding wall of the diaphragm chamber I is transmitted through a lever 28 to a needle 28, which is pivoted on a shaft 30. eedle 29 travels acrossl the faceA of a dial plate 3| upon whose face proper graduations are imprinted. Shaft 30 carries a drum 32 which has fastened to it one end of the flexible element y 33. The other end of the ilexible element is to respond to all movements of the lever 28.

fastened to the outerend of the lever 28. A hair spring 34 is provided for maintaining the flexible element tautI so that the needle 29 is caused It has been the practice to connect theleverv 28 with the yielding wall or. movable end of the diaphragm chamber I8, and, with this understanding, the features of construction just described may be considered for the purpose of the present disclosure as bein-g representative of a lconstruction of a rate of climb instrument in general use.

The relation of the various factors which determine the rate of ow of air through the capillary tube may be expressed by the followingformula:

v8n1 It* where PI is the pressure of 'the air entering the vcapillary-tube and P2 is the pressureof the air leaving the capillary tube; r is the .radius of the orlce; 1I.l ,is the coefllcie'nt of internal friction or viscosity" the air; l is the length of the capillary tube; and v is the volume which flow through the orice in a giventime.

I peratures than it is for higher temperatures.

The viscosity of the air isless for lower tem- It therefore is' apparent' that unless compensation is providedthe diilerence in pressure caused by the'drop in pressure through the orice is less at 'low temperatures than at high temperatures for the same rate of change in altitude, and that because of the greater rate of ow of' air at low temperatures than for high temperatures, an indication dependent upon the rate of flow is too low when low temperatures prevail' if the instru? ment has been'calibrated to indicate correctly at a higher temperature. Conversely; if an instument has been calibrated to indicate correct- 1y at a low temperature, the rate of flow of air through the capillary tube is lesserl at a high Ac temperature than for a lower temperature for the same rate of change in altitudev orpressure and, hence, the instrument would indicate too high.; For the purpose of a clear and concise disclosureof the invention, it will be desirable to referonly to a condition in which the" rate of climb instrument has been calibrated to indicatev properly rat Yso-called high temperatures. which may be taken to bea high average temperature for temperate climates. temperature is, o! course, a matter of convenience and abject to selection.

The reference `An instrument of this character. when carried from the ground by an aircraft is usually exposed to much colder temperatures than ground or laboratory temperatures, especially when it is necessary to fly at high altitudes. At the high ternperatures the viscosity oi' the airis increased y and the instrument, unless corrected, will j give indications of greater rate of change 'in altitude lthan those actually taking place. 'It is therefore `desirable to provide vmeans for automaticaliy decreasing the reading of the rate of climb instrument when such conditions prevail, and, for accomplishing this, I have illustrated in Fig. I a thermostatic element 31 in the form of a bi-metallic member which is carried by lever 28. The free end 38 of the ,thermostatic element is 4pivctecl to the link 39, which likewise is pivotally connected to the post 48a,.rigid1 y mounted `upon the yielding wall of the diaphragm chamber I8.-

Thisthermostatic element is so designed and disposed that its free end 38 moves away' from the pivot 44a of lever 28 upon an increase in tem# perature. Such movement causes the indicating needle 29 to indicate less than `the needle would indicate if no correction were provided forthe higher viscosity of the air at the higher temperature prevailing:` Upon a decrease of the surrOunding temperature, the -free end 38 of ,the

thermostatic element 31 moves toward the pivot dla and increases theeiect of the diaphragm on the indicating means. By such lattery movement of the free end of the element in respect to the fulcrum of its supporting lever the readingv of the indicatingvmeans is increased. It is there fore apparent that the result of undesired influences due to changes of viscosity of the air at diierent temperatures iscorrected. f

.In Fig. III I have shown means by which the compensation may be made in a diierent vm.a,r.-V

ner.

Instead of providing the'thermostatic element 31- in the chain of mechanism, I may prosoY vide said element with a pin i and arrange said element in such a position as to enable said pin to enter or'recede from the mouth of the oriice `42 of the'capillary tube 22. The fastened end of the thermostatic element may be rigidly supported inany manner as, from the capillary.

tube, by meansV of a bracket 44. Since the viscosity of the air decreases'as the 'temperature lowers and the rateof ow through the capillary tube'becomes greater, the rate of flow may be corrected by reducing the cross sectional area or the orifice of the capillary tube. or any part there of. Accordingly, 'the thermostatic element v3`| in Fig'. III. should be ro disposed as to cause pin f M'to move toward the capillary tube asfthe ternperature reducesv and lto move -away fromY the l capillary tube as the temperature=iricreases. At

Va lower temperature than that 'to which' the instrument was' subjected when calibrated, the pin 4i will occupy such a. position as to compen- -sate for the greater rate of flow which would otherwisetake place for the same rate of change in pressure if the efllux of air through the orice were not impeded. Y I

While I have referred in detail to various forms the viscosity of the air may be compensated for in rat of climb instruments, I do not wish to be' restricted to any one embodiment of the invention disclosed, for it i's apparent that changes in relations ot parts and of Vcombinations comeA within the purview of the present invention. To

of devices by which errors due to changes in.

that end I contemplate suchv alterations and A modiiicat-ons as utilise thermostatic means for munication with the atmosphere, indicatingmeans controlled by the yielding wall, and tem'- perature responsive means intermediate said indicating means and yielding wall for correcting peratures.

error in the instrument indication caused vby changes in the viscosity of air from different tem-i 2. A rate of climb indicator for aircraft ccmprising, in combination. a chamber. a second chamber, a yielding wall between said chambers and subject to differential pressures in said chambers, means placing one of said ,chambers in com- `munication with the atmosphere, means placing the other of said chambers in restricted communication with the atmosphere, indicating means controlled by the yielding wall, and means intermediate said indicating means and yielding wall for transmitting the movement of said yicldf ing wall to said indicating means, said inter-- mediate means comprising a thermostatic ele- 1 ment responsive to temperature changes.

3. A rate of climb indicator for aircraft com# prising, in combination, 'a chamber, a second chamber, a yielding wall between said chambers bers, means placing one of said chambers in communication with the atmosphere, means placing, the other 'of said chambers in restricted corn?A munication with the atmosphere, means for in dicatln the mOvement f- Said yielding wall inffhaving a chamber, means communicating said casing with the atmosphere, a movable indicator response to changes in the differential pressures to said chambers, and connecting means intermediate said indicating means and yielding wall, said connecting means comprising a thermostatic. element having one end carried by a pivoted arm and its other end connected with said yielding wall and free to move toward and away fromy the pivot of its carryingarm.

4. A rate of climb indicator for aircraft, comprising, in combination, a chamber, a second" chamber, a yielding wall between said chambers and subject to diiferential pressures in said chambers, means placing one of said chambers. in communication with the atmosphere, means placing the other of said chambers in restricted com` munication with the atmosphere, indicating means controlled by the yielding wall, and means, connecting said indicating means and yielding wall for transmlttingthe movement-of said yielding wall to saidindicating means, saidconnecting'means comprising an element automatically responsive to temperature changes for varying l the indicating relation of the indicating means relative to the position of the-yielding wall for different viscosity conditions oi' the air under the same pressure dinerential.

5. In a rate of climb indicator for aircraft, the combination of an expansible diaphragm device operated in accordance' with changes in altitude, a capillary tube connectedV to the interior of said diaphragm device for providing a restricted flow of air from said device in accordance with` the rate of change of altitude, indicating means operated by said device for indicating said rate of change of altitude. and temperature responsive cases means for aifecting the rate of ow of air through said capillary tube from said diaphragm device in accordance with changes in the viscosity of the air due to changes in temperature.

6. In a'rate of climb indicator, the combination comprising a diaphragm chamber closed from communication with the atmosphere except through the orifice of a capillary tube, means v-controlled by the wall of said diaphragm chamber for indicating its movement when said diaphragm chamber is subjected to changing atmospheric pressure, and thermostatlc means for affecting themovement ot said indicating means in respect to the movement of the wall of the diaphragm chamber and in accordancewith changes in the viscosity of theairgilowing through the capillary tube due to changes in the temperature.

7. In .a rate of climb indicator, the combination of a casing provided with an opening to the atmosphere, an expansible' diaphragm device in said casing, a capillary tube having one end thereof communicating with the interior of said diaphragmdevice and its other end open to the in-x terior of the casing whereby the interior of said diaphragm device is connected lin restricted communication with the atmosphere through said capillary' tube and through the opening in the casing, means for indicating the movement ofthe wallsof said diaphragm device when said device is subjected to changing atmospheric pressure, connecting means between said indicating means and said diaphragm device comprising a lever, a

i-metallic element carried by said lever and ex- 5 tending therefrom, said element being disposed so and subject to differential pressures in said cham- J that its free end movesA to and from the fulcrum -oi' the lever in response to temperature changes,

carried by said casing, 'anexpansible diaphragm in said casing, operating means connecting said diaphragm and said indicator for operating the latter bythe former, a reservoir containing afluid and having communication with said chamber and mounted exteriorlyI of said casing, a tubular connection between the1 interior of said diaphragm and said chamber, avcapillary tube connected to said chamber for providing restricted communication between the interiorof said expansible diaphragm and the atmosphere through said chamber and said casing, and means responsive tc temperature changes for producing a compensating eifect on said indicator in accordance with changes 4in viscosity of the fluid so that said indicator will give true indications irrespective of said changes in viscosity due to changes in temperature.

9. In an instrument for indicating rate of change oi' altitude, a casing, means communicating said casing with the atmosphere, a movable indicator carried by said casing. an expansible diaphragm in said casing,'"operating means connecting said diaphragm and said indicator for operating the latter by the former, a capillary Atube-having a connection to said expansible diaphragm for providing` restricted communication between the interior of said expansible diaphragm and the atmosphere through said casing, and means responsive to temperature changes for producing a compensating ,effect on saidy indicator in accordance with changes in viscosity of air so that said indicator will give true indications in temperature.

v ing the rate 'atwhich pressure on the other-side 4 p d irrespective of 'said' changes in viscosity due to changes'in temperature. i

10. In an instrument for indicating rate of change of altitude,v a casing, meansvc'ommunieating said casing with the atmosphere, a m'ovable indicator carried by said casing, an vexpan-` sible diaphragm in said casing, operating means connecting said diaphragm and said indicator for operating the latter by the'former, a reservoir containing air and having communication with the interior of said diaphragm and mounted exteriorly of said casing, a capillary tube havingV al connection to said diaphragm'and said reservoir for providing restricted communication between the interior of said diaphragm'and the atmos-4 phere .throughsaid casing, and temperature responsive means for producing a compensating effect on said indicator in accordance "with changes in viscosity of air so that said indicator will give true indications irrespective of said changes in viscosity due to changes in temperature.

l1. In combination, an expansible diaphragm having ayielding wall subject to free atmospheric pressure on one side thereof, means for retarding the rate at which pressure on the other side of said yielding wall tends Vto become equal to a Y changing atmospheric pressure due to changes in altitude, indicating lmeans actuated by said yielding wall in i accordance with the rate of -change of altitude, and temperature responsive means for producingv a compensating effect on said indicating means in accordance with changes in viscosity of the atmosphere so that said indicating means will `give .true indications irrespective ot said changes in viscosity due to changes 12. In a rate oi' climb indicator ior aircraft, the combination oi an expansible diaphragm dev ice operated inaccordance with changes in altitude, a capillary tube connected to the interior of said diaphragm device for providing a restricted now of air from said device in accordance with the rate of change of altitude, indicating means operated-by said 'device Iorindicating said rate of change of altitude, and temperature responsive means'for producing acompensating eiect on said indicating means `in accordance with changes in viscosity of air so that said indicating means will give true indications irrespective of said changes in viscosity due to changes in temperature.

`13. Incombination, an expansiblediaphragm having'a yielding wall subject to4 atmospheric pressure on oneside thereof, means for retardof said 'yielding wall tends to become equal to a changing atmospheric pressure due to changes in altitude, indicating `means actuated by` said -yielding wall in accordance with the rate oi' change of altitude, and temperature responsive means for producing a compensating eilect on said indicat-A ing means in accordance with changes in ternperature so that said indicating means will give true indications irrespective of said changes in temperature.

V1i. In combination, Van expansible diaphragm having a yielding wall `subject to atmospheric pressure on one sidethereof, means for retarding the rateat which pressure on the other side of said yielding wall tends lto become equal to a changing atmospheric pressure due to changes ln altitude, indicating means actuated by said yield- *ing wall i'n accordanoewith the rate of change of v Aeases Y altitude, and means connected to said diaphragm for producing a: compensating effect on said indicating means so that the latter will give true indications virrespective of changes in temperature. 15. In combination, an expansible diaphragm pressure on one side thereof, means providing a -restricted passage for retarding the rateat which fpressure on the other side ofy said yielding wall tends to become equal toa changing atmospheric pressure due to changes in altitude, indicating means actuated by said yielding wall in accordance with the rate of change of altitude, means forcontrolling said restricted passage, and temhaving a yielding wall subject to atmospheric perature responsive means for actuating said i controlling means to produce a compensating effeet on said indicating means in accordance with changes in temperature so that said indicating means will give true indications irrespecth'e o! 4said changes in temperature.

16. In combination, an expansible diaphragm having a yielding wall subject to atmospheric pressure on one side thereof, means providing a capillary passage for retarding the rate at which pressure on-the other side of said yielding wall tends to become equal to a changing atmospheric pressure due to changes in altitude, indicating means actuated by said yielding wall in accordance with the rate of change of altitude, valve means for controlling said capillary passage, and temperature responsive means for actuating said valve means to produce a compensating effect on said indicating means in accordance with changes in temperature so that said indicating means will give true indications irrespective of said changes in temperatura 17. In combination; an expansible diaphragm having a'yielding wall subject to. atmospheric pressureY on one side thereof, means providing a restricted passage forretarding the rate at which pressureon theV other side of said yielding wall tends to becomeequal to a changing atmospheric pressureV due to' changesin altitude, indicating means actuated by said yielding wall in 4accordlance with the rate of change of altitude, a reservoir containing air and having communication with the interior of said diaphragm and with the atmosphere through said restricted passage for increasing `the e'ective volume of said diaphragm, automatically actuated means for controlling said restricted passage, and Ameansresponsive tochangesY in temperature ofthe atmosphere for' automatically actuating said controlling means to produce a compensating eiect on said indicating means in accordance with said changes in temperature so that said indicating means will give true indications irrespective of said changes yin temperature.

18. In combinatioman expansible diaphragm having a yielding wall subject to atmospheric pressure on one side thereof, means providing a restricted passage for retarding the rate at which pressure on the other side of said yielding wall tends to become equal to a changing atmospheric pressure duev to changes in altitude, indicating means actuated by said 'yielding wall in accordance with the 'rate of change of altitude, auto- ;matically actuated valve mear: for controlling said restricted passage, and means responsive to changes in temperature for automatically actuating said valve means to produce a compensating l Aeieci; on said indicating means.

ADohF URFER. 

